The traditional method for well-made, water-resistant, walking shoes has been the machine welting process, which is a mechanized version of the older, hand-sewn welting method. A machine welted shoe provides distinct advantages. Because of the indirect attachment of the outer sole to the shoe upper via the welting, the sole can be replaced a number of times, and the repaired shoe has a better shape retention. In addition, a welted shoe is generally more comfortable and water-resistant than non-welted shoe constructions. On the other hand, the production of a machine welted shoe requires a high degree of skill and labor compared to other available methods and demands the use of good quality materials. These factors raise the cost of machine welted shoes considerably.
Traditionally, genuine leather has been the material of choice for shoe welting. Genuine leather has fiber integrity, the orderly arrangement and cross-linkage of natural leather fibers; this fiber integrity gives true leather its notable strength and allows it to withstand the tremendous lateral stresses imposed by the inseaming operation during attachment to the shoe upper and later by Goodyear stitching to the outer sole. Leather welting provides pliability, strength, color, and the fine leather finish which is the marketing attraction of a well-made shoe. Economic conditions, however, have forced the price of genuine leather to extreme levels for many shoe manufacturers. Substitutes have been sought which would provide all the advantages of genuine leather welting and at reduced cost. Current non-leather substitutes for shoe welting include plastic resins, such as polyvinylchloride (PVC), PVC compound derivatives having nitrile rubber content, natural rubbers, and synthetic rubbers, such as neoprene and its derivatives. Such materials provide the requisite pliability and strength for use as shoe welting in Goodyear and Silhouwelt constructed shoes. They do not, however, have the ability to trim and finish like genuine leather welting, and thus are unsuitable for that portion of the shoe market which desires real leather or leather-looking shoes.
Laminated shoe weltings, comprising multiple layers of varying material type, are known. The Fallon U.S. Pat. No. 1,854,183 and Vizard U.S. Pat. No. 2,403,694 describe two-ply laminated weltings having first and second layers of flexible material. Similarly, the patents of Gorman, U.S. Pat. No. 2,114,131; Heft, U.S. Pat. No. 2,023,380; Fallon U.S. Pat. No. 1,762,967; Shaw U.S. Pat. No. 1,188,497; Ridderstrom, U.S. Pat. No. 2,627,079; Wright, U.S. Pat. No. 2,348,583; Hood, U.S. Pat. No. 1,204,769; Sleeper, U.S. Pat. No. RE 19,555; and others, each describe varied laminated shoe weltings comprising two-layer or multiple-layer construction using diverse materials. None, however, provides a two-part wedge bonded shoe welting comprised of non-leather materials which are not ply laminated and can be trimmed and finished like genuine leather.